Secret Cabinet Office papers from the time, now released to the national archives, show he was considered a “subversive”.

The news comes just weeks after the current Tory government’s Trade Union Act came into force, further restricting unions’ ability to represent members and take industrial action.

Macreadie served as deputy general secretary in one of our predecessor unions, CPSA, from 1986 until 1993 and died from a brain tumour in 2010 aged 64.

Our president Janice Godrich wrote in his obituary: “His concentration on organisation, democratic transparency and accountability was an inspiration to many hundreds of union reps in CPSA.”

Commenting on the Morning Star story, our general secretary Mark Serwotka said: “John was a great trade unionist and a friend and, while not at all surprising, it is still shocking to see evidence of Thatcher’s government conspiring against him as part of its wider project to undermine democratic trade unions and reshape society."

Mark added it would be "tempting to think this kind of extreme reaction was in the past, but the parallels with today are obvious", with this Tory government seeking to complete Thatcher’s work through more anti-union legislation and restrictions.